Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:2.7.1.21 (thymidine kinase)
7,561 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A total of 100 herpes simplex viruses isolated from lesions not responding to acyclovir (ACV) therapy were recovered from 51 patients infected with human immunodeficiency virus. In vitro analysis of these isolates included testing their susceptibility to ACV and determining their thymidine kinase (TK) phenotypes. Of the 100 isolates evaluated, 23 were ACV sensitive and 77 were ACV resistant. Seventy-four of these ACV-resistant isolates were of the TK-deficient or low-TK-producer phenotype and three were of the TK-altered phenotype. The TKs isolates that represented each of the different autoradiographic phenotypes were further characterized by enzyme kinetics. The ability of selected isolates to cause disease in vivo was evaluated by using several mouse virulence models. Cutaneous virulence in normal and immunocompromised mice was evaluated, and neurovirulence in normal mice was determined. Latent infections were assayed by the cocultivation of trigeminal ganglia recovered from mice that had survived acute infection. These reactivated viruses were evaluated in vitro and compared with the original infecting isolate. The mechanisms of resistance and pathogenicity of these herpes simplex virus isolates recovered from patients positive for human immunodeficiency virus are similar to those reported for isolates recovered from normal and immunocompromised patients without AIDS.
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PMID:In vitro and in vivo characterization of herpes simplex virus clinical isolates recovered from patients infected with human immunodeficiency virus. 166 96

4'-Azidothymidine (ADRT) is a novel nucleoside analog, that selectively inhibits human immunodeficiency virus replication in human lymphocytes. Unlike the dideoxyribonucleoside analogs and 3'-azido-2',3'-dideoxythymidine (AZT), ADRT retains the 3'-hydroxy group. The pathways of ADRT metabolism were elucidated by determining: (i) the kinetics of the interactions of ADRT and its metabolites with enzymes of thymidine metabolic pathways, (ii) the pool sizes of phosphorylated metabolites, and (iii) the nature of ADRT incorporation into human DNA. ADRT is not a substrate for thymidine phosphorylase, but is metabolized by kinases. Thymidine kinase phosphorylates ADRT to ADRT monophosphate (ADRT-MP). For this enzyme, ADRT has a Ki value of 5.2 microM, in comparison to a Km value of 0.7 microM for thymidine. The Km value of ADRT toward thymidine kinase is 8.3 microM and the rate of ADRT phosphorylation is 1.4% that of thymidine phosphorylation. ADRT-MP has a low affinity toward thymidylate kinase (a Ki value of 28.9 microM versus a Km value of 0.56 microM for thymidylate), and toward thymidylate synthase (a Ki value of 180 microM versus a Km value of 8 microM for deoxyuridylate). The results suggest that ADRT can be activated effectively by cellular kinases without significant interference of normal thymidine metabolism. In cultured human lymphocytes (A3.01, H9, and U937 cells), ADRT was phosphorylated efficiently to ADRT 5'-triphosphate (ADRT-TP), which is the major metabolite of ADRT. The intracellular concentrations of ADRT-TP ranged from 1 to 3.3 microM after 24 h of incubation with 2 microM of ADRT and the half-life of ADRT-TP varied from 3 to 6 h. Although ADRT-TP is a poor competitive inhibitor against dTTP toward DNA polymerases alpha and beta with Ki values of 62.5 and 150 microM, respectively. ADRT-MP was found to be internally incorporated into cellular DNA. The extent of ADRT-MP substitution for dTMP in DNA was 1 in 6979 for A3.01 cells incubated with 2.9 microM ADRT for 24 h. Internal incorporation of ADRT-MP contrasts with the mechanism of other 2',3'-dideoxynucleoside analogs (i.e. AZT, ddC, ddI, d4T...), which are DNA chain terminators. This finding indicates that a 3'-deoxy structure in a nucleoside analog is not a prerequisite for anti-human immunodeficiency virus activity.
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PMID:Metabolism of 4'-azidothymidine. A compound with potent and selective activity against the human immunodeficiency virus. 173 May 94

Infection with human herpesvirus 6 (HHV-6) was found to up-regulate expression of human immunodeficiency virus and human T cell leukaemia virus type I (HTLV-I) long terminal repeat sequence (LTR), and herpes simplex virus type 1 (HSV-1) gD chloramphenicol acetyltransferase (CAT) constructs transfected into the T cell line, J. Jhan. Activation by HHV-6 was due to one or more viral proteins produced early in infection and, in the case of the HTLV-I LTR, was synergistic to induction mediated by the HTLV-I tax gene product. Neither the HTLV-I enhancer nor basal promoter elements of the HSV-1 gD gene were essential for activation and no increase in accumulated HTLV-I mRNA was observed due to HHV-6 infection. Induction by HHV-6 was found to be dependent on the reporter construct used, because the CAT gene and, to a lesser extent, the HSV-1 thymidine kinase gene were responsive to HHV-6 infection although no significant activation of growth hormone constructs was observed. Our results bear a strong resemblance to those obtained for the Epstein-Barr virus BMLF1 gene, indicating that the major HHV-6 trans-activator may be a homologue of this gene.
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PMID:Activation of gene expression by human herpesvirus 6 is reporter gene-dependent. 185 12

Toward gene therapy for the treatment of human immunodeficiency virus type 1 (HIV-1) infections in AIDS, Moloney murine leukemia virus-derived retroviral vectors were engineered to allow constitutive and tat-inducible expression of an HIV-1 5' leader sequence-specific ribozyme (Rz1). These vectors were used to infect the human CD4+ lymphocyte-derived MT4 cell line. The stable MT4 transformants expressing an HIV-1 RNA-specific ribozyme, under the control of the herpes simplex virus thymidine kinase (tk) promoter, were found to be somewhat resistant to HIV-1 infection as virus production was delayed. In cells allowing ribozyme expression under control of the simian virus 40 or cytomegalovirus promoter, the rate of HIV-1 multiplication was slightly decreased, and virus production was delayed by about 14 days. The highest level of resistance to HIV-1 infection was observed in MT4 cells transformed with a vector containing a fusion tk-TAR (trans activation-responsive) promoter to allow ribozyme expression in a constitutive and tat-inducible manner; no HIV-1 production was observed 22 days after infection of these cells. These results indicate that retroviral vectors expressing HIV-1 RNA-specific ribozymes can be used to confer resistance to HIV-1 infection.
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PMID:Resistance to human immunodeficiency virus type 1 (HIV-1) infection in human CD4+ lymphocyte-derived cell lines conferred by using retroviral vectors expressing an HIV-1 RNA-specific ribozyme. 189 2

Rinderpest is a highly contagious viral disease of ruminants with greater than 95% morbidity and mortality. We have constructed an infectious vaccinia virus recombinant that expresses both the fusion (F) gene and the hemagglutinin (H) gene of rinderpest virus. The Wyeth strain of vaccinia virus was used for the construction of the recombinant. Cattle vaccinated with the recombinant virus were 100% protected from challenge inoculation with greater than 1000 times the lethal dose of rinderpest virus. No transmission of recombinant vaccinia virus from vaccinated animals to contact animals was observed. The lyophilized form of vaccinia virus is thermostable and allows circumvention of the logistical problems associated with the distribution and administration of vaccines in the arid and hot regions of Asia and Africa. The insertional inactivation of both the thymidine kinase and the hemagglutinin genes of vaccinia virus led to increased attenuation of the virus; this was manifested by the lack of detectable pock lesions in vaccinated animals. This approach may have wide application in the development of safe and efficacious recombinant vaccines for humans and animals. This becomes quite relevant with the concern of the use of vaccinia virus in a population with high incidence of the human immunodeficiency virus.
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PMID:A vaccinia virus double recombinant expressing the F and H genes of rinderpest virus protects cattle against rinderpest and causes no pock lesions. 189 47

An intragenic enhancer in the pol gene of human immunodeficiency virus type 1 has previously been identified (Verdin et al., Proc. Natl. Acad. Sci. USA 87:4874-4878, 1990). This element is composed of two subdomains both exhibiting phorbol ester-inducible enhancing activity on the viral thymidine kinase promoter in HeLa cells. Examination of the nucleotide sequence of one of these domains (nucleotides 4079 to 4342, HXB2 isolate) revealed the presence of three short DNA regions highly homologous to the recognition site for cellular transcription factor AP-1. Two short oligonucleotides containing these AP-1 sites each functioned as a phorbol ester-inducible enhancer when cloned upstream of the thymidine kinase promoter and transfected into HeLa cells. Gel mobility shift assays and competition experiments using the same two oligonucleotides demonstrated that they bound affinity-purified AP-1 or AP-1 present in uninduced and 12-O-tetradecanoylphorbol-13-acetate-induced HeLa nuclear extracts. Footprinting experiments confirmed that all three predicted sites bound purified AP-1. These results suggest that the AP-1 factor could play a role in the transcriptional regulation of human immunodeficiency virus type 1 gene expression.
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PMID:The intragenic enhancer of human immunodeficiency virus type 1 contains functional AP-1 binding sites. 194 59

The inhibitory effects of a series of antiviral compounds on human immunodeficiency virus type 1 (HIV-1) were evaluated in a plaque assay (PA) in MT-4 cells and a focal immunoassay (FIA) in CD4+ HeLa cells. Similar 50% inhibitory concentrations (IC50) were obtained for the sulfated polysaccharides when measured by PA or FIA: the IC50 values of dextran sulfate and pentosan polysulfate were 0.8 microgram/ml and 0.35 microgram/ml, respectively. Also, comparable IC50 values (ranging from 1.42 to 2.71 microM) were obtained for purine 2',3'-dideoxyribosides (i.e. DDA, DDI and DDG) when evaluated by PA or FIA. In contrast, the IC50 values of pyrimidine 2',3'-dideoxyribosides were invariably 4- to 10-fold lower when monitored by PA than FIA: the IC50s of AZT, D4T and DDC in the PA were 0.015, 0.094 and 0.038 microM, respectively, and in the FIA were 0.062 microM, 0.29 microM and 0.46 microM, respectively. The differential anti-HIV-1 activities found with AZT, D4T and DDC in the PA and FIA systems may at least be related in part to differences in the metabolism of the compounds (i.e. phosphorylation by thymidine kinase or 2'-deoxycytidine kinase) between MT-4 and CD4+ HeLa cells. The novel anti-HIV-1 compounds tetrahydro-imidazo[4,5,1-jk][1,4]-benzodiazepin-2(1H)-thione (TIBO) derivatives, R82150 and R82913, and the acyclouridine derivative 1-[(2-hydroxyethoxy)methyl]-6-phenylthiothymine (HEPT) were also more inhibitory to HIV-1 in the PA than FIA system. The IC50 values of R82150, R82913 and HEPT, as based on PA, were 0.005, 0.003 and 0.79 microM, respectively. Their IC50 values, as based on FIA, were 0.020 microM, 0.015 microM and 3.77 microM, respectively. The TIBO derivatives emerged as the most effective HIV-1 inhibitors of the compounds tested whether assayed by PA or FIA.
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PMID:Anti-HIV-1 activity of antiviral compounds, as quantitated by a focal immunoassay in CD4+ HeLa cells and a plaque assay in MT-4 cells. 198 Jan 26

The development of new antiviral agents has gained increasing momentum. It has kept pace with the identification of specific sites ("targets") in the virus replicative cycle at which potential antiviral drug can interact. The current armamentarium of available antiviral drugs consists of amantadine and rimantadine (against influenza A), ribavirin (against respiratory syncytial virus infection), idoxuridine and trifluridine (against herpetic keratitis), vidarabine and acyclovir (against herpes simplex virus infections), ganciclovir (against cytomegalovirus infections) and Retrovir (against AIDS). Various new compounds have been found which selectively inhibit those viruses [i.e. adenovirus, varicella-zoster virus, thymidine kinase-deficient (TK-) herpes simplex virus strains, and rhinoviruses] that are insensitive or poorly sensitive to the presently available antivirals. Several new compounds have also proven active against human immunodeficiency virus, the causative agent of AIDS; and, as a spin-off of the search for anti-AIDS drugs, new agents may also be expected that are effective against other retrovirus infections as well as hepadnavirus (i.e. hepatitis B virus) infections.
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PMID:New acquisitions in the chemotherapy of viral infections. 216 18

The human immunodeficiency viruses (HIVs) primarily infect CD4+ T lymphocytes, leading eventually to the development of a systemic immune dysfunction termed acquired immunodeficiency syndrome (AIDS). An attractive strategy to combat HIV-mediated pathogenesis would be to eliminate the initial pool of infected cells and thus prevent disease progression. We have engineered a replication-defective, conditionally cytotoxic adenovirus vector, Ad-tk, whose action is dependent on the targeted expression of the herpes simplex virus type 1 thymidine kinase gene (tk), cloned downstream of the HIV-1 long terminal repeat, in human cells expressing the HIV-1 transcriptional activator Tat. Infection of Tat-expressing human HeLa or Jurkat cells with Ad-tk resulted in high-level tk expression, which was not deleterious to the viability of these cells. However, in the presence of the antiherpetic nucleoside analog ganciclovir, Ad-tk infection resulted in a massive reduction in the viability of these Tat-expressing cell lines. As adenoviruses are natural passengers of the human lymphoid system, our results suggest adenovirus vector-based strategies for the targeted expression, under the control of cis-responsive HIV regulatory elements, of cytotoxic agents in HIV-infected cells for the therapy of HIV-mediated pathogenesis.
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PMID:Selective induction of toxicity to human cells expressing human immunodeficiency virus type 1 Tat by a conditionally cytotoxic adenovirus vector. 224 44

Four patients with human immunodeficiency virus (HIV) infection who received chronic oral acyclovir therapy for suppression of recurrent varicella zoster or herpes simplex virus infection developed persistent disseminated hyperkeratotic papules that failed to heal with intravenous or high-dose oral acyclovir therapy. Varicella zoster virus, resistant to acyclovir in vitro, was isolated from skin lesions of all four patients. Three patients were adults in whom the acquired immunodeficiency syndrome (AIDS) had been diagnosed 12 to 20 months before isolation of acyclovir-resistant varicella zoster virus. The fourth patient was a perinatally HIV-infected child who developed primary varicella infection at age 7 years when profoundly immunosuppressed (absolute CD4+ lymphocyte count less than 50 cells/microL). Mean antiviral susceptibilities (ED50 values) of the four clinical isolates compared with the ED50 values of the reference strain Oka were 85 compared with 3.3 mumol/L for acyclovir, 1.4 compared with 0.8 mumol/L for vidarabine, and 123 compared with 117 mumol/L for foscarnet. When assayed by [125I]-dC plaque autoradiography, 90% to 100% of the viral isolate populations had altered or no measurable thymidine kinase function. Acyclovir-resistant varicella zoster virus infection may complicate long-term oral acyclovir administration in patients with AIDS and may be associated with the appearance of atypical hyperkeratotic papules.
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PMID:Acyclovir-resistant varicella zoster virus infection after chronic oral acyclovir therapy in patients with the acquired immunodeficiency syndrome (AIDS). 229 95


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